Robust rotation measurement (rotation transducer)
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From: dclist on 31 Jul 2010 18:31 I'm looking for a way to do moderately robust angular displacement (and angular velocity) measurement. I was trying to use quadrature encoders but it appeared the sensors were occasionally missing some state transitions possibly due to the discs moving too quickly or some occasional optical occlusion. I am therefore looking for alternatives. What are commonly used alternatives to measuring angular displacement?
From: krw on 31 Jul 2010 18:49 On Sat, 31 Jul 2010 15:31:29 -0700 (PDT), dclist <dclist(a)gmail.com> wrote: >I'm looking for a way to do moderately robust angular displacement >(and angular velocity) measurement. I was trying to use quadrature >encoders but it appeared the sensors were occasionally missing some >state transitions possibly due to the discs moving too quickly or some >occasional optical occlusion. I am therefore looking for alternatives. What sort of rates would an LED/photo-diode not track? >What are commonly used alternatives to measuring angular displacement? I saw a cute Hall-effect rotary encoder this week. The output was 360-degree, with any sort of encoding desired (mag-dir, quadrature, binary,...). http://www.austriamicrosystems.com/eng/Products/Magnetic-Encoders/Rotary-Encoders
From: Tim Wescott on 31 Jul 2010 18:49 On 07/31/2010 03:31 PM, dclist wrote: > I'm looking for a way to do moderately robust angular displacement > (and angular velocity) measurement. I was trying to use quadrature > encoders but it appeared the sensors were occasionally missing some > state transitions possibly due to the discs moving too quickly or some > occasional optical occlusion. I am therefore looking for alternatives. > > What are commonly used alternatives to measuring angular displacement? I've had very good luck with encoders in the past. If it's a good quality encoder, you're not going too fast for the encoder, and you haven't screwed up your decoding in the electronics or the software, then about the only ways left to have problems are that you're abusing the encoder somehow. Resolvers are a good alternative to encoders. Good quality pots are not to be sneered at. RVDT's work well over limited stroke lengths. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com Do you need to implement control loops in software? "Applied Control Theory for Embedded Systems" was written for you. See details at http://www.wescottdesign.com/actfes/actfes.html
From: Tim Wescott on 31 Jul 2010 19:15 On 07/31/2010 03:49 PM, krw(a)att.bizzzzzzzzzzzz wrote: > On Sat, 31 Jul 2010 15:31:29 -0700 (PDT), dclist<dclist(a)gmail.com> wrote: > >> I'm looking for a way to do moderately robust angular displacement >> (and angular velocity) measurement. I was trying to use quadrature >> encoders but it appeared the sensors were occasionally missing some >> state transitions possibly due to the discs moving too quickly or some >> occasional optical occlusion. I am therefore looking for alternatives. > > What sort of rates would an LED/photo-diode not track? > >> What are commonly used alternatives to measuring angular displacement? > > I saw a cute Hall-effect rotary encoder this week. The output was 360-degree, > with any sort of encoding desired (mag-dir, quadrature, binary,...). > > http://www.austriamicrosystems.com/eng/Products/Magnetic-Encoders/Rotary-Encoders If I'm not mistaken Allegro Microsystems has those, too. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com Do you need to implement control loops in software? "Applied Control Theory for Embedded Systems" was written for you. See details at http://www.wescottdesign.com/actfes/actfes.html
From: Tim Wescott on 31 Jul 2010 19:17
On 07/31/2010 03:49 PM, krw(a)att.bizzzzzzzzzzzz wrote: > On Sat, 31 Jul 2010 15:31:29 -0700 (PDT), dclist<dclist(a)gmail.com> wrote: > >> I'm looking for a way to do moderately robust angular displacement >> (and angular velocity) measurement. I was trying to use quadrature >> encoders but it appeared the sensors were occasionally missing some >> state transitions possibly due to the discs moving too quickly or some >> occasional optical occlusion. I am therefore looking for alternatives. > > What sort of rates would an LED/photo-diode not track? There is an upper limit that you ignore at your peril. The ones with open-collector outputs have, I think, a more severe speed limit* than ones with totem-pole or CMOS output. * And, obviously, more sensitivity to your supporting circuitry. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com Do you need to implement control loops in software? "Applied Control Theory for Embedded Systems" was written for you. See details at http://www.wescottdesign.com/actfes/actfes.html |